It is a new attempt to apply the case based reasoning(CBR) method to the pattern CAD domain.This paper presents a case based model for pattern design.We first decompose the pattern into pattern elements

and represents the pattern case by frame-based case structure and element-based case data

then the procedure of pattern design is modeled as the case-making process of specific pattern case frame aiming to various pattern elements.We also present some new solving strategy for the key techniques used in CBR

such as the organization and query mechanics of case base

case adoption and re-design of case etc.Meanwhile

the conductive interaction technique based on design context and the knowledge-based promotion from local operation to global layout are applied successfully in the model.Running the prototype system shows that CBR is an effective approach for the design of serial and regular pattern.